Alternating-current apparatus.



!I-To. 853,106; PATBNTED MAY '7, 1907. R. D. MERSHON.

ALTERNATING CURRENT APPARATUS.

APPLIOATION IILED P123. 1, 1904. RENEWED APR. 10, 1907.

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1/ Flyfi' i i i i i i i i i Wiinesses: A, Invenior No. 853,106. PATENTED MAY 7, 1907. R. D. MERSHON. ALTERNATING CURRENT APPARATUS.

APPLICATION FILED FEBJ, 1904. RENEWED APR. 10, 1907.

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PATENTED MAY 7, 1907.

R. D. MERSHON. ALTERNATING CURRENT APPARATUS.

APPLICATION FILED FEB. 1, 1904. nmwnwsn APR. 10. 1907.

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A. Inventor UNITED sTArEs PATENT OFFICE.

RALPH D. MERSHON, or NEW YORK, N. Y.

ALTERNATlNG-QURRENT APPARATUS- Specification of Letters Patent.

Application filed February 1, 1904. Renewed April 10, 1907. Serial No. 367,336-

] taining a desired magnetic flux distribution,

as, for example, a simple sine distribution or an approximation thereto, in electrical ap paratus, and in another co-pending application,Serial Number 190,440, I have described a method of varying the speed of a motor 7 while producing therein a desired flux distribution, or maintaining a distribution within certain limits of approximation to that desired. In the latter application there is also described a novel plan for constructing the apparatus so. as to ,\produce a desired flux wave, or a close approximation thereto, in the secondary circuit, although the flux distribution in the rimary may be such that otherwise it wou dnot produce in the secondary the desired wave or such close approximation thereto. The principle on which this lan is based is that the flux wave in the secondary circuits. may be modified or varied according to the width of the electric arc embraced by those circuits; and the; present invention therefore consists, broadly stated, in a motor in which, the widths of the secondar circuits are proportioned for the purpose oKmodifying the flux wave therein.

For a more com lete understanding of the invention I have s own in the accompanying drawing a typical embodiment, selecting for that purpose a secondary of the squirrel cage type. It should be understood, howi ever, that the invention is not limited to such a construction, but may be embodied in other forms of whatever type. a

In the drawing, Figure 1 represents diagrammatically a two-pole motor, with one ead per pole, the two leads being 180 apart,

and 5o bution therein.

ig. 2 shows the curve of the flux distri- Fig. 3 shows the flux waves, produced by the flux distribution of Fig. 2, in secondary circuits of widths embracing 180, 90, and respectively. Fig. 4 represents diagrammatically a motor having two poles, produced by currents led in at two points per pole; Fi 5 shows the. flux distribution therein, produced thereby in secondary circuits of 60, and 30, respectively. Fig. 7 re resents a sigiirrel cage secondary as ordinari y constructe and Fig. 8 one in which my present invention is embodied. Fig. 9 represents a motor in which the flux distribution may be varied. and the number of poles made two, four or six, with a secondary element havin circuits embracing 180 electrical degrees Tor the six pole connection, and 60 electrical degrees for thetwo pole connection.

Patented May 7,1907.

Referring now to Fig. 1, U represents the winding of a two pole motor with one lead per 'pole, the leads being 180 apart. The resultin flux distribution in the motor will be as in icated by the curve a, in which electrical degrees are plotted on the horizontal axis, from d to d, being 180 degrees, and flux intensity on the vertical axis. The curves a, a m, Fig. 3, represent the flux waves genere ated by the flux distribution of curve a, in

secondary coils whose widths are such that they embrace 180, 90 and 60 electrical degrees respectively. The points on the horizontal axis of these curves represent the ositions of the middle points of their respective coils. 'These positions correspond to those, on the horizontal axis of the-curve u, at which the flux intensity values represented by the ordinates of u aremeasured. The vertical ordinates of u, a and a represent not flux intensity as in u, but the total flux through the coils corresponding to the ositions of their centers. In other words, if in the magnetic field of the motor U the flux distribution of which is represented by the curve a, we rotate an electric circuit whose width is 180, the flux wave in this circuit will be the curve a. If-the width ofthe circuit is 90- the flux wave in it will be 41. and of 60, the curve a Thedotted curve, u,-is a simple sine wave, assuming, that this IS the wave that it is desired to approximate.

It will be noted that the curve a, for the 180 circuit, and 11. for the 90, fall on opposite sides of the sine wave a. This shows that for all arcs between 180 and 90, the flux waves are closer approximations to the simple sine wave than lseitheru or ta and that somewhere between the arcs mentioned there is some width of circuit which will have in it a flux wave which isexactly, or which very closely approximates, a simple sine wave. This curve may be found by trial or degrees and degrees of arc'are identical.

' explanation already given in regard to the flux distribution wave, and the flux wave, will apply equall well to a motor with a greater number 0 poles, provided it be borne in mind in this case that the arcs mentioned are all electrical. In other words, if we should feed currents into the motor so as to roduce four poles instead of two, the flux distribution curve a would still be obtained, but the distance dd, instead of being 180 degrees of arc, would be 180 electrical degrees, which in the-case of the fourpoles corresponds to 90 degrees of are. It should also be borne in mind that if with the fourpole connection we have a secondary circuit embracing 180 electrical degrees and thus having in it a iiux wave corresponding to u, and that if we change from four poles to two oles, the same secondary circuit, which hetore embraced 180 electrical degrees, will then embrace only 90 electrical degrees, and will have in it the flux wave of. Also,if for the fOlT- ole connection we employ that width of circuit between 180 and 90 electrical degrees which will give the close approximation to a simple sine flux wave as previously described, then on changing the number of poles to two the flux wave in this secondary will depart more from the simple sine Wave than does a because the secondary now embraces less than 90 electrical degrees.

An explanation similar to that alreadygiven for Figs. '1, 2. and 3 will apply to Figs. 4, 5, and 6, but the latter represent conditions when two currents per pole are fed to the motor instead of one, as for exam le, in the motor V, so spaced that the resu ting flux distribution is that shown by curve 22. The corresponding flux waves for the distribution v, in secondary circuits embracing 90, and 30 electrical degrees, are exemplified by curves 1), o 12 respectively. Here, as before, the dotted curve, 1), represents the simple sine wave which it is desired to approximate. In the case of 'v the difference be tween the two is'so small that they are practically coincident. It will be seen that 12 also closel ap roximates a simple sine wave. It there ore ollows that circuits of 'widths between 90 and 60 electrical degrees will have in them flux waves'ver close .to tliesimple sine wave. Of course t e curves v, e '0 are egually representative for a greater number 0 poles, it being remembered, as before, that the arcs concerned are in every case electrical.

Fig. 7 represents a s uirrel cage secondary element as it is ordinari y constructed, at the same time utilizing all the available copper space. The bars are all short circuited to a fore be obtained by a proper connection orspacing of the circuits, or both, as convenient.

It should 'be understood,- of course, that instead of bars and their end connectionswe maiy use coils of any number of convolutions.

Fig. 9 I have shown a system in which my invention is a plied, the arran ement of the connections, eads, and controdler being such as to ive six, four and two poles in the motor. T e stationary element of the motor, W, is shown as a uniformly distributed Gramine ring, though of course the kind of winding, whether ring or drum, uniformly or not uniformly distributed, is immaterial, per se,'to the invention. It is also immaterial to the present invention how a given flux distribution is obtained or varied, when the production of a certain distribution'or variation of distribution is desired, or how the poles are produced, or their number varied when such variation is desired; The leads to the motor-are eight in number, as shown, brought out to contacts T. The single phase source of power is indicated by S, and a controller is diagrammatically illustrated at C. It will be seen on tracing out the connections that in the first position of the controller the motor Willhave six poles, with one lead per pole,

in the second position will have four poles,

also with one lead per pole, and in the thirdposition will have two poles with two leads per pole. The secondary element E has its circuits so connected, as will be seen by tracing the conductors,-that they embrace arcs of 180 electrical degrees when the motor is connected for six poles and they therefore have in them the flux curve for that are shown in Fig. 3.

On changing to four poles the flux waves in these circuits will be those corresponding to and will, therefore lie between a and a Fig. 3, and will be nearer the sine Wave than either of the latter; and on chang' ing to two poles the flux. wave will be that corresponding to curve v of Fig. 6. If instead of feeding in the current at two points per pole in the two pole connections it had een led in at only one point per ole, as be- IIO fore, the resulting flux wave woul .have been that of a Fig. 3, which for the purpose of this explanation we will consider as too great adeparture from the approximation to a sine it being also assumed for this explanation modi on, account of the lar e number of poles and tribution in the primary rality of leads my invention,

' tiomng the Widths of the secondary means for varying wave which we are endeavoring to maintain,

that the flux waves for the other two connections do not exceed the limits of allowable departure from the sine flux wave. Hence on chan ing to the two pole connection we also I the flux distribution in the primary to produce another and better flux Wave in the secondar For a olyphase motor the sets of leads'i or, each p0 e would be repeated for each phase, or each phase introduced into the motor by a set of leads with the common use of some or all of them for different phases.

The system just described exemplifies one of the most important advantages of the invention. It will be noted that if the secondary in Fig. 9 were connected in the ordinary way, the flux wave therein when the number of oles is six would not fall'between a and u, ut would be u, more nearly approximating in form the distribution curve u, Fig. 2. To produce a better wave it would therefore be necessar to modifythe flux distribution by leading in the current or currents at two or more oints per ole, thus requiring at least twe ve leads or the six poles. -On changing to four poles and to two poles the flux" waves) would be still closer approximations to the distribution curve a, and a pluper pole would still be required. But by properly proportioning the widths of the secondary circuits according to we are able to obtain a ood wave in those circuits with only one lea per pole inboth the six and the four pole connections, the two leads er pole becoming necessary, in this particu ar case, only in the two pole connect1on. Weare therefore able to materially reduce the total number of leads to the motor.

Other systems in which my present invention is embodied might be illustrated, but the principle of the invention will be readily understood from the explanation already given. One instance in which the invention will be of particular value is that of a slow vs eed motor, in which it is ordinarily diflicult or impossible to secure a good flux distribution consequently few coi s or turns per pole-in the primary winding. By properly proporcircuits, however, in accordance with my invention, the flux wave in these circuits may be greatly imp'oved.

hat I claim is: 1. In alternating current apparatus, the combination with the primary element and the number of poles therein, of a secondary element having the width of its circuits proportioned, as to the arcs embraced thereby, to produce a predetermined flux wave therein with the magnetic flux disfor one of the possible number of poles, as set forth.

- 1n the primary,

flux distribution in 2. In alternating current apparatus, the combination with the rimary element, means for producing diflerent numbers of poles therein and means for producing a given magnetic fiux distribution in the primary for one of the possible numbers of poles, of a secondary element having the width of its circuits proportioned, as to the arcs embraced thereby, to produce a predetermined flux wave therein with the given flux distribution in the primary, as set forth.

'3. In alternating current apparatus, in combination, a primary element, means for producing diilerent numbers of poles therein, means for producing a given magnetic flux distribution in the primary with a particular number of poles, a secondary element having the widthof its circuits proportioned as to the arcs embraced thereby to produce a predetermined flux wave therein with the given flux distribution, and means for varying the flux wave in the secondary, as set forth.

4. In alternating current apparatus, in combination, a primary element, means for producing different numbers of poles therein, means for producing a given magnetic flux distribution in the primary with a particular number of poles, a secondary element having the width of its circuits proportioned as to the arcs embraced thereby to produce a predetermined flux wave therein with the given flux distribution, and means for varying the flux distribution in the primary, as set forth.

5. In alternating current apparatus, in

combination, a primary element, means for producing a particular number of magnetic poles therein, means for producing a given ma netic flux distribution in the primary wit the particular number of poles, a secondary element having the width of its circuits proportioned as to the arcs embraced thereby to produce a predetermined flux wave therein with the given flux distribution in the primary for the particular number of oles, means for varying the number of poles and means for varying the fiux distribution in the primary, as set forth.

6. In alternating current apparatus, in

combination, a primary element, means for roducing a particular number of poles therein, means for producing a given magnetic the primary for the particular number of poles, a secondary element having the width of its circuits proportioned as to the arcs'embraced thereby to produce a predetermined flux wave therein with the given flux distribution in the primary for the particular number of oles, means for varying the number of po es in the primary and means for simultaneously varying the flux distribution in the primary, as set forth.

7. -In alternating current apparatus, in

combination, a primary element, means "for reducing a particular number of poles there- 1n, means for producing a given flux distribution in the primary with the particular number of poles, a secondary element having the width of its circuits proportioned as to the arcs embraced therebv to produce a predetermined Ilux wave therein with the given flux distribution in theprimary for the par-' ticular number of )oles, means for varying the number of poles in the primary, and means for restoring the flux wave to that predetermined, or a close approximation thereto. as set forth.

8. in an alternating current motor, in mmbinatiou, a primary winding or windings, supply leads thereto to produce a particular number of poles therein and a given magnetic flux distribution, a secondary element having the width of its circuits proportioned, as to the arcs embraced thereby, to produce a predetermined fiux wave in such circuits with the given flux distribution in the primary for the particular number of poles, and

vmeans for varying the number of poles by varying the points of connection of the supply loads, as set forth.

9. In an alternating current motor, in combination, a primary winding or windin s, supply leads thereto to. produce a particu ar number of poles therein and a given flux distribution, a secondary element having the width of its circuits proportioned as to the arcs embraced thereby to produce a predetermined llux wave therein with the given flux distribution in the primary, and means for varying the number of poles in the primary by leading in current or currents thereto at aplurality of points per pole, the number of points being chosen to give a flux distribution with the new number or numbers of poles which will maintain the flux Wave in the secondary the same or within predetermined limits of departure therefrom, as set forth.

10. in an alternating current motor, in combination, a primary winding or windings, supply leads thereto to produce a particular number of .poles therein and a given flux distribution, 'a secondary element having the width of its circuits proportioned, as to the arcs embraced thereby, to produce a predetermined flux wave therein with the given flux distribution in the primary, and means .each 0 the said numbers of for varying the number of poles in the primary by leading in current or currents thereto 1 at different points and with different num- 1 poles which will )roduee in the secondar the predetermined ux wave or a desire approximation thereto, as set forth.

11. In an alternating current motor, in combination, a primary Winding or windings, supply leads thereto to produce a particular number of oles therein and a given mag netic flux (llSil'ibUtiOll, a secondary element having the width of its circuits proportioned, as to the arcs embraced thereby, to produce a predetermined flux wave therein with the given flux distribution in the primary, and means for varying the number of poles in the primary by leading in current or currents thereto at different points a' pluralit of points per pole, whereby the flux distribution in the primary will be maintained the same or a close approximation thereto, as set forth.

12. In an alternating current motor, in combination, a primary element, means for producing diil'erent numbers of poles therein, a secondary element having the width of its circuits proportioned as to the arcs embraced thereby to produce a' flux Wave therein for each oi the said numbers of poles which shall fall within predetermined limits, means for producing other number or numbers of poles, and means for varying the magnetic flux distribution in-the rimary with the new number or numbers opoles to vary the flux wave in the secondary, as set forth.

13. In an alternating current motor, in combination, a primary element, means for producing diiierent numbers of poles therein, a secondary element having the width of its circuits proportioned as to the arcs embraced thereb to produce a flux wave therein for poles which shall fall within predetermined hmits, means for producing other number or numbers of poles, and means for .varying the magnetic flux distribution in the primary with the new numher or numbers of oles to maintain the flux wave in the secon ary within said predetermined limits, as set forth.

S. S. DUNHAM,

Lewis. 

